1. Field of the Invention
The present invention relates to a light guide plate and manufacturing method thereof. More particularly, the present invention relates to a light guide plate fabricated by a transfer process.
2. Description of Related Art
Due to the rapid development of semiconductor devices and man-machine interfaces, multi-media systems have found wide applications. In the past, cathode ray tube (CRT) is a dominant type of displays on the market because of its superb display quality and low production cost. However, from an environmental point of view, CRT tends to consume too much power, requires too much material to fabricate and always produces hazardous radiation in the process of operation. Hence, with considering the production of light, compact, low power rating, radiation free and high picture quality, liquid crystal display (LCD) has rapidly become the mainstream display product on the market.
Since the liquid crystal panel is not self-illuminant, a back light module must be installed accompanying with it to serve as a source of illumination. Aside from cold cathode fluorescent lamp (CCFL), light-emitting diode (LED) is another type of light source for a back light module.
FIG. 1 is a side view of a conventional back light module assembly. As shown in FIG. 1, a back light module 100 mainly comprises a light guide plate 110, a light source 120, at least a reflector 130 and a plurality of optical films 140. The light provided by the source 120 enters the light guide plate 110 through a light incident surface S1 and then reflects by a bottom surface S2 before emerging from a light output surface S3. Thus, through the light guide plate 110, light from the light source 120 is transformed into a planar light source suitable for illuminating a liquid crystal panel.
To increase the uniformity of the planar light source produced by the back light module 100, molds for forming the light guide plate 110 are often etch or electro-etched to produce a protrusion patterns. After performing an injection molding, a protrusion pattern 112 is formed on the bottom surface S2 of the light guide plate 110. Hence, light emitted from the light source 120 will be scattered by the protrusion pattern 112 on the bottom surface S2 to produce a planar light source with a high degree of uniformity. However, this method of fabricating the light guide plate is rather complicated and frequently affects other processing parameters (for example, the flow drag of molding compound affected by the protrusion pattern, the homogeneity of etching, the cooling rate and so on). Consequently, the reproducibility of the fabricated light guide plate 110 is rather low and product yield is hardly improved.
In an alternative method, a light-scattering pattern is printed onto the bottom surface S2 of the light guide plate 110. However, the printing process has to be carried out after the light guide plate 110 has formed rather than in tandem.
In addition, a reflector 130 is often attached to the bottom surface S2 of the light guide plate 110 to increase the brightness of the planar light source provided by the back light module 100. Nevertheless, attaching the reflector 130 to the light guide plate 110 increases not only processing time and production cost, but also the overall thickness of the back light module 100. Furthermore, even if reflector 130 are attached to the areas outside the light incident surface S1 and the light output surface S3 of the light guide plate 110, the possibility of light leak from gaps between the light guide plate 110 and various reflectors 130 cannot be completely eliminated. Therefore, the conventional method of fabricating a light guide plate needs some improvements before an ultra-high brightness and ultra-thin liquid crystal display can be produced.